1. Field of the Invention
This invention relates to a dynamic elastomeric seal assembly and extrusion backup for use between reciprocal tubular members, such as a shiftable piston and stationary sleeve in an oil well tool, such as a safety valve, hydraulically actuated packer or sliding sleeve.
2. Description of the Prior Art
The standard T-seal and backup configuration used on downhole well tools is shown and identified as prior art in FIG. 7. These standard configurations comprise an elastomeric primary seal having a T-shaped cross-section which can be positioned within an annular groove in either an inner or outer concentric tubular member. The narrower tip section generally extends beyond the seal receptacle groove to establish sealing contact with a polished seal surface. The width of the groove is generally equal to the width of the enlarged base section of the T-seal.
In some applications it is necessary to provide extrusion backups for a conventional T-seal. As shown in the prior art in FIG. 7, cylindrical backup members can be positioned within the groove of the seal receptacle with the cylindrical backup members being positioned adjacent the tip section and above the base of the seal member. These conventional T-seal configurations have proven to be very reliable in many conventional well tool applications. However, at elevated pressure and temperatures extrusion can occur causing a dynamic seal failure. With the conventional dynamic T-seal configuration, the cylindrical backup members are also supported by the base of the elastomer and radial loads are transmitted through the cylindrical backup members to the more elastic base section of the primary seal. These radial loads can produce an eccentric or uneven load or squeeze on the elastomeric T-seal, and the seal will be heavily loaded at one position and more relaxed or even leaking at the radially opposite position. Even if this radial loading does not cause the seal to leak, undesirable vibration problems can occur during shifting of the movable piston and the life of the T-seal can be reduced. The instant invention provides an improved dynamic seal configuration in which cylindrical extrusion backups also serve to center the shiftable piston and retain the dynamic seal in place with an even load distribution providing a uniform squeeze on the seal member.